We have discovered that the human pituitary contains novel mammary mitogens that stimulate growth of human breast cancer and normal human mammary cells in culture and synergize with estrogens to induce mammary growth and development in hypophysectomized castrated, sexually immature rats and monkeys. The responsible factor(s) is a heat labile peptide which is not hPRL, hGH, or FGF. The object of this proposal is to further characterize this substance(s) and purify it from human pituitary glands after depletion of hPRL and hGH by affinity chromatography with monoclonal antibodies to hPRL and hGH. Six different bioassays including 3 in vitro systems and 3 in vivo ones will be used to insure specificity, determine whether there is a single or multiple factors, and also ascertain whether growth of mammary cancers is affected by the same substances that induce growth and development of the normal mammary gland. The bioassays include: 1) MCF-7 cells, 2) WRK-1 cells, 3) normal human mammary cells, 4) hyophysectomized and castrated E2-treated male rats, 5) hypophysectomized athymic nude mice harboring MCF-7 cell tumors, and 6) hypophysectomized castrated sexually immature male rhesus monkeys. Techniques to isolate the mammary mitogen(s) will include gel filtration, ion-exchange chromatography, HPLC, isoelectric focusing and production of monoclonal antibodies. Amino acid analysis and protein sequencing is also envisaged. Studies will be carried out to determine whether the effect of this novel mammary mitogen(s) requires the synergy of estradiol or estradiol-like substances or whether the effects of these two factors are separate. These studies will help us better understand how the pituitary gland controls the growth of mammary cancer and the normal mammary gland and help determine whether the factor(s) that stimulate growth of malignant mammary tissue is the same as the one(s) that induces growth of normal tissue. We further hope to isolate one or more novel mammary mitogens in pure form and suggest that identification of such a substance(s) may help us design novel and effective therapies for breast cancer.